tags 27016 + patch
quit

Michael Heerdegen <michael_heerdegen@web.de> writes:

> npostavs@users.sourceforge.net writes:
>
>> I hope someone will correct me if I've gotten mixed up again, but I
>> believe the byte-compiled case already works fine:
>>
>>     ~/src/emacs$ cat bug-27016-defsetf.el
>>     (require 'cl)
>>
>>     (defvar pair nil)
>>     (setq pair (cons 3 4))
>>     (when nil
>>       (defalias 'foobar 'cons)
>>       (defsetf foobar setcar))
>>     ~/src/emacs$ emacs -Q -batch -f batch-byte-compile bug-27016-defsetf.el
>>
>>     In toplevel form:
>>     bug-27016-defsetf.el:1:1:Warning: cl package required at runtime
>>     bug-27016-defsetf.el:3:1:Warning: global/dynamic var ‘pair’ lacks a prefix
>>     ~/src/emacs$ emacs -Q -batch -l bug-27016-defsetf.elc --eval '(setf (foobar pair) 0)'
>>     Symbol’s function definition is void: \(setf\ foobar\)
>
> Yes - if you use two separate Emacs instances.  The defsetf gets
> evaluated in the Emacs that is used to compile the code
> (unconditionally).
>
> So what you state is not suspicious for a problem with a surprising side
> effect when performing macroexpansion, right?

Right.

    ~/src/emacs$ emacs -Q -batch --eval '(byte-compile-file "bug-27016-defsetf.el")' -l bug-27016-defsetf.elc --eval  '(progn (setf (foobar pair) 0) (print pair))'

    In toplevel form:
    bug-27016-defsetf.el:1:1:Warning: cl package required at runtime
    bug-27016-defsetf.el:3:1:Warning: global/dynamic var ‘pair’ lacks a prefix

    (0 . 4)

You were indeed correct to point to that FIXME comment in
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=27016#28

Here's a patch for it: